title: In vivo analysis of Argos structure-function. Sequence requirements for inhibition of the Drosophila epidermal growth factor receptor.
abstract: The Drosophila Argos protein is the only known extracellular inhibitor of the epidermal growth factor receptor (EGFR). It is structurally related to the activating ligands, in that it is a secreted protein with a single epidermal growth factor (EGF) domain. To understand the mechanism of Argos inhibition, we have investigated which regions of the protein are essential. A series of deletions were made and tested in vivo; furthermore, by analyzing chimeric proteins between Argos and the activating ligand, Spitz (a transforming growth factor-alpha-like factor), we have examined what makes one inhibitory and the other activating. Our results reveal that Argos has structural requirements that differ from all known EGFR activating ligands; domains flanking the EGF domain are essential for its function. We have also defined the important regions of the atypical Argos EGF domain. The extended B-loop is necessary, whereas the C-loop can be replaced with the equivalent Spitz region without substantially affecting Argos function. Comparison of the argos genes from Drosophila melanogaster and the housefly, Musca domestica, supports our structure-function analysis. These studies are a prerequisite for understanding how Argos inhibits the Drosophila EGFR and provide a basis for designing mammalian EGFR inhibitors.
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.
authors.forename: R
authors.initials: R
authors.lastname: Howes
authors.forename: J D
authors.initials: JD
authors.lastname: Wasserman
authors.forename: M
authors.initials: M
authors.lastname: Freeman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence / Q000235:genetics; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000737:chemistry* / Q000196:embryology; D004815:Epidermal Growth Factor; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D005123:Eye / Q000254:growth & development / Q000648:ultrastructure; D005136:Eye Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D006793:Houseflies / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics; D016415:Sequence Alignment; D017384:Sequence Deletion / Q000235:genetics; D013329:Structure-Activity Relationship; D014921:Wings, Animal / Q000254:growth & development
chemical_list: D029721:Drosophila Proteins; D005136:Eye Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; C075638:aos protein, Drosophila; C076026:spi protein, Drosophila; D004815:Epidermal Growth Factor; D066246:ErbB Receptors